The worst blackout in US history has moved improvement of the nation's electrical grid to the top of Washington's fall policy agenda.

Congress is already planning a range of hearings into what went wrong, while administration officials are calling again for passage of the mammoth energy bill now plodding through the legislative process.

They involve such hot-button questions as whether federal regulation of local markets is appropriate, or stifling. Moreover, the nature of the US electrical system is such that its problems defy simple solutions. Old-fashioned regional utilities work next to unfettered commercial power firms, all using transmission lines erected in the era of rotary phones. Thus whatever Washington does in coming months will probably be - at best - a partial fix.

"Everyone has understood for a long time there are some serious problems with the power system," says Bruce Everett, an energy expert at Tufts University's Fletcher School of Law and Diplomacy.

Experts don't know yet exactly what caused last Thursday's rolling blackout. The crisis may, or may not, have begun with the failure of an Ohio power line. Instability in the Northeastern electrical grid may have exacerbated this problem.

In the end, determining why the blackout spread might be more important than pinpointing its trigger. In theory the nation's electrical system is supposed to isolate such a blackout. The fact that it did not means there may be faults in the US grid's contagion prevention system. "Things go wrong quite a lot, but they're usually geographically contained," says Peter VanDoren, an expert on electricity issues at the Cato Institute.

But even without definitive reports on the blackout's nature, Washington was moving already to address known or perceived faults in the US electrical system. One move appears to have strong bipartisan support: giving more enforcement power to the now-voluntary industry group that oversees electrical transmission standards.

The group, the North American Electric Reliability Council (NERC), was created after a major blackout hit the Northeast in 1965. It is supposed to set transmission standards for all utilities to meet - but currently compliance with those standards is voluntary. NERC has long lobbied for the power to levy mandatory sanctions, and both senior Democrats and the White House now agree that giving the group some teeth might help head off future system problems.

"We need to pass an energy bill that gives the Federal Energy Regulatory Commission the authority to impose mandatory reliability standards," said Secretary of Energy Spencer Abraham this week.

Yet establishment of such authority is not foreordained, since the GOP and congressional Democrats differ as to whether new powers for NERC should be a stand-alone bill, or included in the overarching energy package that will be the subject of a House-Senate conference this fall.

Many Democrats would like a NERC upgrade passed quickly, by itself. But Republicans generally favor keeping it in the omnibus energy package, as leverage to help push through more controversial provisions such as authority to allow drilling in the Arctic National Wildlife Refuge. "The Republicans will most likely stay the course and use last week's outage to continue the momentum to move a [comprehensive] bill out of conference," says a Democratic congressional staff member.

Then there's the controversial issue of the extent of government intervention in electrical transmission markets. President Bush's own appointee to head the Federal Energy Regulatory Commission, Pat Wood III, has called for the establishment of regional grid managers to improve the flow of power nationwide.

But some regions, such as the Northwest, believe regional mangers might interfere with their own relatively self-contained systems. Top administration officials are thus now backing away from their own agency official's regional management proposals.